Я сяду на скамейку у входа.

Я сяду means I will sit down.

Russian makes a clear distinction between:

• сидеть = to be sitting
• сесть / сяду = to sit down

So this sentence focuses on the action of taking a seat, not the state of already being seated.

Compare:

• Я сяду на скамейку у входа. = I’ll sit down on the bench by the entrance.
• Я буду сидеть на скамейке у входа. = I’ll be sitting on the bench by the entrance.

In English, sit can sometimes cover both ideas, but Russian usually separates them.

сяду is the 1st person singular future form of сесть.

So:

• сесть = to sit down
• я сяду = I will sit down

This verb is perfective, so its simple future form is used for a completed one-time action.

A few related forms:

• я сяду = I will sit down
• ты сядешь = you will sit down
• он / она сядет = he / she will sit down

This is an important verb to memorize because its forms are not very transparent for beginners.

Because the sentence describes movement toward a surface.

With на, Russian usually uses:

• accusative for motion onto something
• prepositional for location on something

Here, скамейку is the accusative singular of скамейка, because the meaning is:

• I will sit down onto the bench

Compare:

• Я сяду на скамейку. = I will sit down on the bench.
  (motion → accusative)

• Я сижу на скамейке. = I am sitting on the bench.
  (location → prepositional)

This is a very common pattern in Russian.

Russian uses на because a bench is treated as a surface you sit on.

So:

• на скамейку = onto the bench
• на скамейке = on the bench

This matches English fairly closely here. You sit on a bench, so Russian also uses the preposition meaning on/onto.

У входа means by the entrance or near the entrance.

The preposition у normally takes the genitive case, so:

• вход = entrance
• входа = genitive singular

So literally:

• у входа = by the entrance / near the entrance

This is a very common structure:

• у двери = by the door
• у окна = by the window
• у дома = by the house

Usually it means by the entrance or near the entrance.

In English, the best translation depends on context:

• by the entrance
• near the entrance
• sometimes at the entrance

Russian у often suggests physical proximity, not necessarily being exactly inside the entrance area.

So скамейка у входа is the bench located near the entrance.

Yes, but the meaning changes.

• Я сяду на скамейку у входа. = I will sit down on the bench by the entrance.
  Focus: the action of taking a seat.

• Я буду сидеть на скамейке у входа. = I will be sitting on the bench by the entrance.
  Focus: the state or ongoing situation.

So the original sentence is about the moment of sitting down, not about remaining seated.

Because the verb сесть already includes that meaning.

Russian often builds this idea directly into the verb:

• сидеть = be sitting
• сесть = sit down

So сяду already contains the idea of down or into a seated position.

That is why Я сяду is enough; you do not need another word corresponding to English down.

Yes. Russian word order is flexible, though the neutral order here is very natural:

• Я сяду на скамейку у входа.

You could also say:

• У входа я сяду на скамейку.
• На скамейку у входа я сяду.

These versions are grammatically possible, but they shift emphasis:

• У входа first emphasizes the location
• На скамейку у входа first emphasizes where exactly you will sit

For a basic neutral statement, the original word order is best.

The stress is:

Я ся́ду на скаме́йку у вхо́да.

Word by word:

• ся́ду
• скаме́йку
• вхо́да

Stress matters in Russian, so it is worth learning it together with the word.

Usually, yes: скамейка means bench.

It is the normal word for a bench in a park, by a building, near an entrance, and so on.

In this sentence, на скамейку у входа naturally means onto the bench by the entrance.

Not always.

Russian often drops subject pronouns when the verb form already shows who the subject is. So both are possible:

• Я сяду на скамейку у входа.
• Сяду на скамейку у входа.

Both mean I will sit down on the bench by the entrance.

Including Я can sound more explicit or contrastive, for example:

• Я сяду на скамейку, а ты стой здесь.
  = I’ll sit on the bench, and you stay here.

In isolation, keeping Я is perfectly natural and beginner-friendly.